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android_system_core/fs_mgr/libdm/dm.cpp

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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "libdm/dm.h"
#include <linux/dm-ioctl.h>
#include <sys/ioctl.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <chrono>
#include <functional>
#include <string_view>
#include <thread>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/macros.h>
#include <android-base/strings.h>
#include <uuid/uuid.h>
#include "utility.h"
namespace android {
namespace dm {
using namespace std::literals;
DeviceMapper::DeviceMapper() : fd_(-1) {
fd_ = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC));
if (fd_ < 0) {
PLOG(ERROR) << "Failed to open device-mapper";
}
}
DeviceMapper& DeviceMapper::Instance() {
static DeviceMapper instance;
return instance;
}
// Creates a new device mapper device
bool DeviceMapper::CreateDevice(const std::string& name, const std::string& uuid) {
if (name.empty()) {
LOG(ERROR) << "Unnamed device mapper device creation is not supported";
return false;
}
if (name.size() >= DM_NAME_LEN) {
LOG(ERROR) << "[" << name << "] is too long to be device mapper name";
return false;
}
struct dm_ioctl io;
InitIo(&io, name);
if (!uuid.empty()) {
snprintf(io.uuid, sizeof(io.uuid), "%s", uuid.c_str());
}
if (ioctl(fd_, DM_DEV_CREATE, &io)) {
PLOG(ERROR) << "DM_DEV_CREATE failed for [" << name << "]";
return false;
}
// Check to make sure the newly created device doesn't already have targets
// added or opened by someone
CHECK(io.target_count == 0) << "Unexpected targets for newly created [" << name << "] device";
CHECK(io.open_count == 0) << "Unexpected opens for newly created [" << name << "] device";
// Creates a new device mapper device with the name passed in
return true;
}
bool DeviceMapper::DeleteDeviceIfExists(const std::string& name,
const std::chrono::milliseconds& timeout_ms) {
if (GetState(name) == DmDeviceState::INVALID) {
return true;
}
return DeleteDevice(name, timeout_ms);
}
bool DeviceMapper::DeleteDeviceIfExists(const std::string& name) {
return DeleteDeviceIfExists(name, 0ms);
}
bool DeviceMapper::DeleteDevice(const std::string& name,
const std::chrono::milliseconds& timeout_ms) {
std::string unique_path;
if (!GetDeviceUniquePath(name, &unique_path)) {
LOG(ERROR) << "Failed to get unique path for device " << name;
}
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_REMOVE, &io)) {
PLOG(ERROR) << "DM_DEV_REMOVE failed for [" << name << "]";
return false;
}
// Check to make sure appropriate uevent is generated so ueventd will
// do the right thing and remove the corresponding device node and symlinks.
CHECK(io.flags & DM_UEVENT_GENERATED_FLAG)
<< "Didn't generate uevent for [" << name << "] removal";
if (timeout_ms <= std::chrono::milliseconds::zero()) {
return true;
}
if (unique_path.empty()) {
return false;
}
if (!WaitForFileDeleted(unique_path, timeout_ms)) {
LOG(ERROR) << "Timeout out waiting for " << unique_path << " to be deleted";
return false;
}
return true;
}
bool DeviceMapper::DeleteDevice(const std::string& name) {
return DeleteDevice(name, 0ms);
}
static std::string GenerateUuid() {
uuid_t uuid_bytes;
uuid_generate(uuid_bytes);
char uuid_chars[37] = {};
uuid_unparse_lower(uuid_bytes, uuid_chars);
return std::string{uuid_chars};
}
bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table, std::string* path,
const std::chrono::milliseconds& timeout_ms) {
std::string uuid = GenerateUuid();
if (!CreateDevice(name, uuid)) {
return false;
}
// We use the unique path for testing whether the device is ready. After
// that, it's safe to use the dm-N path which is compatible with callers
// that expect it to be formatted as such.
std::string unique_path;
if (!LoadTableAndActivate(name, table) || !GetDeviceUniquePath(name, &unique_path) ||
!GetDmDevicePathByName(name, path)) {
DeleteDevice(name);
return false;
}
if (timeout_ms <= std::chrono::milliseconds::zero()) {
return true;
}
if (!WaitForFile(unique_path, timeout_ms)) {
LOG(ERROR) << "Timed out waiting for device path: " << unique_path;
DeleteDevice(name);
return false;
}
return true;
}
bool DeviceMapper::GetDeviceUniquePath(const std::string& name, std::string* path) {
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
PLOG(ERROR) << "Failed to get device path: " << name;
return false;
}
if (io.uuid[0] == '\0') {
LOG(ERROR) << "Device does not have a unique path: " << name;
return false;
}
*path = "/dev/block/mapper/by-uuid/"s + io.uuid;
return true;
}
std::optional<DeviceMapper::Info> DeviceMapper::GetDetailedInfo(const std::string& name) const {
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
return std::nullopt;
}
return Info(io.flags);
}
DmDeviceState DeviceMapper::GetState(const std::string& name) const {
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
return DmDeviceState::INVALID;
}
if ((io.flags & DM_ACTIVE_PRESENT_FLAG) && !(io.flags & DM_SUSPEND_FLAG)) {
return DmDeviceState::ACTIVE;
}
return DmDeviceState::SUSPENDED;
}
bool DeviceMapper::ChangeState(const std::string& name, DmDeviceState state) {
if (state != DmDeviceState::SUSPENDED && state != DmDeviceState::ACTIVE) {
return false;
}
struct dm_ioctl io;
InitIo(&io, name);
if (state == DmDeviceState::SUSPENDED) io.flags = DM_SUSPEND_FLAG;
if (ioctl(fd_, DM_DEV_SUSPEND, &io) < 0) {
PLOG(ERROR) << "DM_DEV_SUSPEND "
<< (state == DmDeviceState::SUSPENDED ? "suspend" : "resume") << " failed";
return false;
}
return true;
}
bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table) {
std::string ignore_path;
if (!CreateDevice(name, table, &ignore_path, 0ms)) {
return false;
}
return true;
}
bool DeviceMapper::LoadTableAndActivate(const std::string& name, const DmTable& table) {
std::string ioctl_buffer(sizeof(struct dm_ioctl), 0);
ioctl_buffer += table.Serialize();
struct dm_ioctl* io = reinterpret_cast<struct dm_ioctl*>(&ioctl_buffer[0]);
InitIo(io, name);
io->data_size = ioctl_buffer.size();
io->data_start = sizeof(struct dm_ioctl);
io->target_count = static_cast<uint32_t>(table.num_targets());
if (table.readonly()) {
io->flags |= DM_READONLY_FLAG;
}
if (ioctl(fd_, DM_TABLE_LOAD, io)) {
PLOG(ERROR) << "DM_TABLE_LOAD failed";
return false;
}
InitIo(io, name);
if (ioctl(fd_, DM_DEV_SUSPEND, io)) {
PLOG(ERROR) << "DM_TABLE_SUSPEND resume failed";
return false;
}
return true;
}
// Reads all the available device mapper targets and their corresponding
// versions from the kernel and returns in a vector
bool DeviceMapper::GetAvailableTargets(std::vector<DmTargetTypeInfo>* targets) {
targets->clear();
// calculate the space needed to read a maximum of kMaxPossibleDmTargets
uint32_t payload_size = sizeof(struct dm_target_versions);
payload_size += DM_MAX_TYPE_NAME;
// device mapper wants every target spec to be aligned at 8-byte boundary
payload_size = DM_ALIGN(payload_size);
payload_size *= kMaxPossibleDmTargets;
uint32_t data_size = sizeof(struct dm_ioctl) + payload_size;
auto buffer = std::unique_ptr<void, void (*)(void*)>(calloc(1, data_size), free);
if (buffer == nullptr) {
LOG(ERROR) << "failed to allocate memory";
return false;
}
// Sets appropriate data size and data_start to make sure we tell kernel
// about the total size of the buffer we are passing and where to start
// writing the list of targets.
struct dm_ioctl* io = reinterpret_cast<struct dm_ioctl*>(buffer.get());
InitIo(io);
io->data_size = data_size;
io->data_start = sizeof(*io);
if (ioctl(fd_, DM_LIST_VERSIONS, io)) {
PLOG(ERROR) << "DM_LIST_VERSIONS failed";
return false;
}
// If the provided buffer wasn't enough to list all targets, note that
// any data beyond sizeof(*io) must not be read in this case
if (io->flags & DM_BUFFER_FULL_FLAG) {
LOG(INFO) << data_size << " is not enough memory to list all dm targets";
return false;
}
// if there are no targets registered, return success with empty vector
if (io->data_size == sizeof(*io)) {
return true;
}
// Parse each target and list the name and version
// TODO(b/110035986): Templatize this
uint32_t next = sizeof(*io);
data_size = io->data_size - next;
struct dm_target_versions* vers =
reinterpret_cast<struct dm_target_versions*>(static_cast<char*>(buffer.get()) + next);
while (next && data_size) {
targets->emplace_back(vers);
if (vers->next == 0) {
break;
}
next += vers->next;
data_size -= vers->next;
vers = reinterpret_cast<struct dm_target_versions*>(static_cast<char*>(buffer.get()) +
next);
}
return true;
}
bool DeviceMapper::GetTargetByName(const std::string& name, DmTargetTypeInfo* info) {
std::vector<DmTargetTypeInfo> targets;
if (!GetAvailableTargets(&targets)) {
return false;
}
for (const auto& target : targets) {
if (target.name() == name) {
if (info) *info = target;
return true;
}
}
return false;
}
bool DeviceMapper::GetAvailableDevices(std::vector<DmBlockDevice>* devices) {
devices->clear();
// calculate the space needed to read a maximum of 256 targets, each with
// name with maximum length of 16 bytes
uint32_t payload_size = sizeof(struct dm_name_list);
// 128-bytes for the name
payload_size += DM_NAME_LEN;
// dm wants every device spec to be aligned at 8-byte boundary
payload_size = DM_ALIGN(payload_size);
payload_size *= kMaxPossibleDmDevices;
uint32_t data_size = sizeof(struct dm_ioctl) + payload_size;
auto buffer = std::unique_ptr<void, void (*)(void*)>(calloc(1, data_size), free);
if (buffer == nullptr) {
LOG(ERROR) << "failed to allocate memory";
return false;
}
// Sets appropriate data size and data_start to make sure we tell kernel
// about the total size of the buffer we are passing and where to start
// writing the list of targets.
struct dm_ioctl* io = reinterpret_cast<struct dm_ioctl*>(buffer.get());
InitIo(io);
io->data_size = data_size;
io->data_start = sizeof(*io);
if (ioctl(fd_, DM_LIST_DEVICES, io)) {
PLOG(ERROR) << "DM_LIST_DEVICES failed";
return false;
}
// If the provided buffer wasn't enough to list all devices any data
// beyond sizeof(*io) must not be read.
if (io->flags & DM_BUFFER_FULL_FLAG) {
LOG(INFO) << data_size << " is not enough memory to list all dm devices";
return false;
}
// if there are no devices created yet, return success with empty vector
if (io->data_size == sizeof(*io)) {
return true;
}
// Parse each device and add a new DmBlockDevice to the vector
// created from the kernel data.
uint32_t next = sizeof(*io);
data_size = io->data_size - next;
struct dm_name_list* dm_dev =
reinterpret_cast<struct dm_name_list*>(static_cast<char*>(buffer.get()) + next);
while (next && data_size) {
devices->emplace_back((dm_dev));
if (dm_dev->next == 0) {
break;
}
next += dm_dev->next;
data_size -= dm_dev->next;
dm_dev = reinterpret_cast<struct dm_name_list*>(static_cast<char*>(buffer.get()) + next);
}
return true;
}
// Accepts a device mapper device name (like system_a, vendor_b etc) and
// returns the path to it's device node (or symlink to the device node)
bool DeviceMapper::GetDmDevicePathByName(const std::string& name, std::string* path) {
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
PLOG(WARNING) << "DM_DEV_STATUS failed for " << name;
return false;
}
uint32_t dev_num = minor(io.dev);
*path = "/dev/block/dm-" + std::to_string(dev_num);
return true;
}
bool DeviceMapper::GetDeviceNumber(const std::string& name, dev_t* dev) {
struct dm_ioctl io;
InitIo(&io, name);
if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
PLOG(WARNING) << "DM_DEV_STATUS failed for " << name;
return false;
}
*dev = io.dev;
return true;
}
bool DeviceMapper::GetDeviceString(const std::string& name, std::string* dev) {
dev_t num;
if (!GetDeviceNumber(name, &num)) {
return false;
}
*dev = std::to_string(major(num)) + ":" + std::to_string(minor(num));
return true;
}
bool DeviceMapper::GetTableStatus(const std::string& name, std::vector<TargetInfo>* table) {
return GetTable(name, 0, table);
}
bool DeviceMapper::GetTableInfo(const std::string& name, std::vector<TargetInfo>* table) {
return GetTable(name, DM_STATUS_TABLE_FLAG, table);
}
// private methods of DeviceMapper
bool DeviceMapper::GetTable(const std::string& name, uint32_t flags,
std::vector<TargetInfo>* table) {
std::vector<char> buffer;
struct dm_ioctl* io = nullptr;
for (buffer.resize(4096);; buffer.resize(buffer.size() * 2)) {
io = reinterpret_cast<struct dm_ioctl*>(&buffer[0]);
InitIo(io, name);
io->data_size = buffer.size();
io->data_start = sizeof(*io);
io->flags = flags;
if (ioctl(fd_, DM_TABLE_STATUS, io) < 0) {
PLOG(ERROR) << "DM_TABLE_STATUS failed for " << name;
return false;
}
if (!(io->flags & DM_BUFFER_FULL_FLAG)) break;
}
uint32_t cursor = io->data_start;
uint32_t data_end = std::min(io->data_size, uint32_t(buffer.size()));
for (uint32_t i = 0; i < io->target_count; i++) {
if (cursor + sizeof(struct dm_target_spec) > data_end) {
break;
}
// After each dm_target_spec is a status string. spec->next is an
// offset from |io->data_start|, and we clamp it to the size of our
// buffer.
struct dm_target_spec* spec = reinterpret_cast<struct dm_target_spec*>(&buffer[cursor]);
uint32_t data_offset = cursor + sizeof(dm_target_spec);
uint32_t next_cursor = std::min(io->data_start + spec->next, data_end);
std::string data;
if (next_cursor > data_offset) {
// Note: we use c_str() to eliminate any extra trailing 0s.
data = std::string(&buffer[data_offset], next_cursor - data_offset).c_str();
}
table->emplace_back(*spec, data);
cursor = next_cursor;
}
return true;
}
void DeviceMapper::InitIo(struct dm_ioctl* io, const std::string& name) const {
CHECK(io != nullptr) << "nullptr passed to dm_ioctl initialization";
memset(io, 0, sizeof(*io));
io->version[0] = DM_VERSION0;
io->version[1] = DM_VERSION1;
io->version[2] = DM_VERSION2;
io->data_size = sizeof(*io);
io->data_start = 0;
if (!name.empty()) {
snprintf(io->name, sizeof(io->name), "%s", name.c_str());
}
}
std::string DeviceMapper::GetTargetType(const struct dm_target_spec& spec) {
if (const void* p = memchr(spec.target_type, '\0', sizeof(spec.target_type))) {
ptrdiff_t length = reinterpret_cast<const char*>(p) - spec.target_type;
return std::string{spec.target_type, static_cast<size_t>(length)};
}
return std::string{spec.target_type, sizeof(spec.target_type)};
}
static bool ExtractBlockDeviceName(const std::string& path, std::string* name) {
static constexpr std::string_view kDevBlockPrefix("/dev/block/");
if (android::base::StartsWith(path, kDevBlockPrefix)) {
*name = path.substr(kDevBlockPrefix.length());
return true;
}
return false;
}
bool DeviceMapper::IsDmBlockDevice(const std::string& path) {
std::string name;
if (!ExtractBlockDeviceName(path, &name)) {
return false;
}
return android::base::StartsWith(name, "dm-");
}
std::optional<std::string> DeviceMapper::GetDmDeviceNameByPath(const std::string& path) {
std::string name;
if (!ExtractBlockDeviceName(path, &name)) {
LOG(WARNING) << path << " is not a block device";
return std::nullopt;
}
if (!android::base::StartsWith(name, "dm-")) {
LOG(WARNING) << path << " is not a dm device";
return std::nullopt;
}
std::string dm_name_file = "/sys/block/" + name + "/dm/name";
std::string dm_name;
if (!android::base::ReadFileToString(dm_name_file, &dm_name)) {
PLOG(ERROR) << "Failed to read file " << dm_name_file;
return std::nullopt;
}
dm_name = android::base::Trim(dm_name);
return dm_name;
}
std::optional<std::string> DeviceMapper::GetParentBlockDeviceByPath(const std::string& path) {
std::string name;
if (!ExtractBlockDeviceName(path, &name)) {
LOG(WARNING) << path << " is not a block device";
return std::nullopt;
}
if (!android::base::StartsWith(name, "dm-")) {
// Reached bottom of the device mapper stack.
return std::nullopt;
}
auto slaves_dir = "/sys/block/" + name + "/slaves";
auto dir = std::unique_ptr<DIR, decltype(&closedir)>(opendir(slaves_dir.c_str()), closedir);
if (dir == nullptr) {
PLOG(ERROR) << "Failed to open: " << slaves_dir;
return std::nullopt;
}
std::string sub_device_name = "";
for (auto entry = readdir(dir.get()); entry; entry = readdir(dir.get())) {
if (entry->d_type != DT_LNK) continue;
if (!sub_device_name.empty()) {
LOG(ERROR) << "Too many slaves in " << slaves_dir;
return std::nullopt;
}
sub_device_name = entry->d_name;
}
if (sub_device_name.empty()) {
LOG(ERROR) << "No slaves in " << slaves_dir;
return std::nullopt;
}
return "/dev/block/" + sub_device_name;
}
bool DeviceMapper::TargetInfo::IsOverflowSnapshot() const {
return spec.target_type == "snapshot"s && data == "Overflow"s;
}
} // namespace dm
} // namespace android
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